FIELD OF THE INVENTION
The invention relates to an apparatus and to a method for heating a liquid or viscous medium, in particular a polishing agent for a chemical mechanical polishing. Furthermore, the invention relates to an apparatus for polishing, in particular for a chemical mechanical polishing of wafers.
Depending on the strength of the chemical component of the polishing process, the temperature during chemical mechanical polishing (CMP) has a decisive influence on the process result. In this case, the process temperature, that is to say the temperature on the side of the wafer to be polished during the polishing operation, is influenced essentially by three thermal components: 1) the frictional heat occurring during the polishing process; 2) the heating of the polishing table; and 3) the temperature of the polishing agent (slurry).
The frictional heat produced during the polishing process can be influenced only in a limited manner, since the polishing pressure and the rotational speeds of the table and the carrier are generally subject to other process preconditions. Heating for the polishing table is usually provided in the apparatuses for polishing.
A specific and defined setting of the temperature of the polishing agent has so far not been taken into consideration. If the temperature of the polishing agent is controlled at all, this is done in such a way that the conduit for the polishing agent is guided through the heating device which is responsible for the temperature control of the polishing table. Such heating has, however, the disadvantage that it is not possible for the polishing agent and the polishing table to be heated independently.
In a further known apparatus, a heating coil is wound around the conduit for the polishing agent. However, this has the disadvantage that by comparison with the desired temperature of the polishing agent the heating coil operates at very high temperatures in order to be able to react quickly to temperature fluctuations. However, this can lead locally to very high temperatures in the polishing agent and thus to a degradation of the polishing agent.